Spontaneous reticulum cell sarcoma (RCS) and methylcholanthrene (MCA)-induced tumors of SJL/J mice will be used as a model for the study of alterations of MHC transplantation antigens (loss or gain). Enriched and purified preparations of spontaneous and early in vivo passaged RCS tumor cells, as well as MCA-induced tumors will be examined, 'respectively' for H-2 expression using a panel of monoclonal antisera. Parameters such as the identity of the tissue source from which tumor cells are isolated and the degree of tumor progression at the time of isolation will also be investigated. Serological analyses to be used for H-2 antigenic characterization will be dye exclusion cytotoxicity, cytostasis, immunofluorescence, absorption analysis, and blocking test. Cell mediated lympholysis (CML) studies will also be done. Biochemical characterization of the unexpected antigens, using immunoprecipitation and sequential immunoprecipitation in SDS-PAGE analysis, and 2-dimensional-gel electrophoresis will provide data for comparison with normal H-2K or D region gene products. Additional support has been sought to examine the biological relevancy of all alterations which are noted. These studies therefore will give insight into the correlation between altered H-2 expression and the ultimate fate of a tumor cell population as well as the mechanisms by which such alterations might occur.